Chronicling the link between scent and memory

Anyone who remembers a vacation to the beach when they breathe in the ocean air or who thinks of their grandmother when they smell homemade cookies is well aware that scent is strongly connected to memories.
But what is the mechanism that triggers this trip down memory lane?

A process known as long-term potentiation describes how synapses change in
strength
following brief periods of activity. It has long been cited to explain how mammals store different
types of information—such as specific places, names and events—and has been observed in
almost every part of the brain, with one glaring exception: the olfactory bulb,
the area that processes the sense of smell.

In the June 2009 issue of Nature Neuroscience, however, Ben W. Strowbridge, PhD,
associate professor of neurosciences at Case Western Reserve University School of Medicine,
and Yuan Gao, a PhD student, show that olfactory brain circuits actually
do change with experience—providing a possible explanation for how animals form memories
of particular scents.

"Scientists commonly believe that the brain processes information in a way that is something like
climbing a pyramid: Simple sensory information is at the base of the pyramid; more complex concepts,
such as recognition of a person's face, are generated in higher areas of the brain," Dr. Strowbridge
says. He goes on to explain that he and Gao found that in olfactory learning, higher brain centers
may first make a prediction about what a scent could be. They then engage the most appropriate brain
circuits to test that prediction against incoming sensory data. "We proved that in olfactory
learning there is much more talking back-and-forth from the top of the pyramid to the
bottom than we had previously thought."